New Kotlin Standard: What Awaits Developers in 2025

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New Kotlin Standard: What Awaits Developers

The JetBrains team has officially introduced an updated standard for the Kotlin language, which fundamentally changes the approach to development. The release of Kotlin 2.0, known as the K2 project, brings not only a new compiler but also a whole range of architectural improvements. Let's break down the key changes awaiting developers and how to prepare for migration.

Main Innovation: The K2 Compiler

The heart of the new standard is the K2 compiler. It has been completely rewritten from scratch and provides:

Compilation speed — 2-3 times faster than the previous version. This is especially noticeable in large projects.
Improved type inference — the compiler determines data types more accurately, reducing the number of errors during development.
Clean architecture — the new compiler frontend and backend simplify adding new features in the future.

Multiplatform Becomes the Standard

Kotlin Multiplatform (KMP) is now an official part of the language, not experimental. Developers can write shared code for Android, iOS, Web (Kotlin/JS), and the server side (Kotlin/JVM) without duplicating logic. This is expected to lead to a boom in cross-platform applications using Kotlin.

Changes in Syntax and API

The new standard introduces several long-awaited syntax improvements:

Flexible constructors — the ability to use default values and named arguments in constructors without restrictions.
Improved work with collections — new functions like mapNotNull, flatMapSequence and optimizations for Sequence.
Stable inline classes — they now work predictably and do not require the @JvmInline annotation.

What Does This Mean for the Community?

Transitioning to the new standard will require updating tools: IntelliJ IDEA, Android Studio, and the Gradle plugin. JetBrains promises 99% backward compatibility, but some outdated APIs (e.g., kotlinx.coroutines versions below 1.7) will need to be updated. For developers, this means:

Faster CI/CD pipelines due to quicker compilation.
A lower entry barrier for beginners thanks to clearer error messages.
The ability to create truly cross-platform projects without workarounds.

When to Expect the Stable Release?

At the time of writing, Kotlin 2.0 is in the Release Candidate stage. JetBrains plans to release the final version in the first quarter of 2025. Developers are recommended to start testing their projects on the beta version now to avoid surprises during migration.

The new Kotlin standard is not just an update, but an evolution of the language. It is becoming faster, safer, and more versatile. If you are not yet familiar with Kotlin, now is the best time to start, and if you already write in it, get ready for an upgrade.